Stator-Flux-Oriented Fault-Tolerant Control of Flux-Switching Permanent-Magnet Motors

Flux-switching permanent-magnet (FSPM) motors are a newly developed brushless AC (BLAC) machine having magnets in the stator. This paper proposes and implements a stator-flux-oriented (SFO) control strategy for fault-tolerant operation of FSPM motors. The key is to set the q-axis component of armature current invariant before and after the fault. In the rotor reference frame, by building a SFO-dq equation of the FSPM motor, the fault-tolerant control strategy is deduced. The finite-element method and the field-circuit cosimulation method are employed to analyze the performance of the FSPM motor drive. Finally, a dSPACE-based FSPM motor drive platform is built for experimental verification. Both the steady-state and dynamic performances at normal and fault-tolerant operations are tested, confirming that the proposed fault-tolerant operation can keep the output torque invariant while offering good dynamic performance during fault.

I. Introduction

Fault tolerance of motor drives is important for critical applications desiring continued operation following a fault such as electric vehicle applications [1]. In recent years, some fault-tolerant machines, namely the switched reluctance (SR) machine [2] and the conventional permanent-magnet (PM) brushless machine having magnets in the rotor (the rotor-PM machine) [3], have been developed. However, the SR machine still suffers from relatively low power density, while the rotor-PM machine is still hindered by weak mechanical structure [4]. Recently, a new class of brushless machines with PMs located in the stator, namely the stator-PM machine, has been proposed, which offers high power density and good mechanical integrity [5]–[7]. It has been identified that the doubly-salient PM (DSPM) motor can inherently offer fault tolerance [8], [9]. On the other hand, recent research has verified that the power density of a flux-switching PM (FSPM) motor is significantly higher than that of a DSPM motor [10]. Hence, how to improve the fault-tolerance capability of FSPM motors has attracted more and more attention.